1. Field
Embodiments of the present invention relate to a booklet, particularly a booklet having an anti-counterfeiting function, and more particularly, to a kind of booklet such as a passport in which a high security function is necessary.
2. Description of the Related Art
As shown in FIG. 11, in a medium such as a passport and a bankbook, a plurality of sheets 81 and 82 overlap each other, and center portions thereof are saddle-stitched with an iron wire or a thread 83, whereby a booklet shape is obtained. Particularly, in a kind of booklet such as a passport in which high security for anti-counterfeiting is required, a binding thread 83 (anti-counterfeiting binding thread), which is treated with a fluorescent dye and thus emits light with an ultraviolet light source, is used for anti-counterfeiting (Japanese Unexamined Patent Application, First Publication No. 2001-305078).
On the other hand, in recent years, a booklet has been developed in which an IC chip storing individual information or the like as digital data is buried so as to realize reading-out or writing-in with respect to the IC chip with a reader or writer. Particularly, in an electronic passport field, such a booklet has been adopted in various countries. As for burying an IC chip in a booklet, a type in which an IC chip is attached to a booklet cover, and a type in which an inlet including an IC chip is interposed between pages and both pages are adhered to each other have been proposed (Japanese Unexamined Patent Application, First Publication No. 2005-88569).
In the type in which the inlet including the IC chip is interposed between pages, particularly, in the case of saddle-stitching, an innermost sheet at which the saddle-stitching thread is exposed is folded in half with the saddle-stitching thread made as a center, and the inlet is interposed in the innermost sheet. In this type, a uniform load is applied to both pages, and thus this type is preferable from viewpoints of a manufacturing process and strength. This type has been adopted as a passport of several countries including Japan (http://www.mofa.go.jp/mofaj/toko/passport/pdfs/ic_leaflet.pdf).
It is necessary to record individual face image information in the IC chip on the basis of International Civil Aviation Organization (ICAO) standard that defines specifications of the electronic passport. Furthermore, when face image information recorded in the IC chip and a face image recorded on a sheet of the passport in a photograph type or the like are compared with each other, the electronic information and the visual recognition information are mutually confirmed, and thus anti-counterfeiting and security are improved.
However, rewriting of the information recorded in the IC chip or replacement of the IC chip itself may occur. Furthermore, the passport may be counterfeited by re-covering the face photograph on the sheet of the passport. Therefore, improvement of security such as prevention of rewriting of the IC chip, and improvement in a technology of preventing counterfeiting of the visual recognition information are preferable.
As a technology of preventing the counterfeiting of the visual recognition information, Japanese Unexamined Patent Application, First Publication No. 2001-232978 discloses a passport in which the visual information such as the face image is buried in a sheet as a latent image and this visual information is viewed using a polarization film so as to verify the visual information such as the face image. According to a method of Japanese Unexamined Patent Application, First Publication No. 2001-232978, compared to the face photograph, it is difficult to counterfeit the face image due to the latent image, and thus security is improved. However, in the method of Japanese Unexamined Patent Application, First Publication No. 2001-232978, a verifying mechanism including a separate polarization film is also necessary.
In consideration of the above problems in the related art, an object of embodiments of the present invention is to provide a booklet in which security is improved by providing a latent image for anti-counterfeiting and self-verification of the latent image for anti-counterfeiting is possible in a yet easier manner.